Phenol and cyclohexanone are important compounds in the chemical industry and are useful in, for example, production of phenolic resins, bisphenol A, ε-caprolactam, adipic acid, and plasticizers.
Currently, a common route for the production of phenol is the Hock process. This is a three-step process in which the first step involves alkylation of benzene with propylene to produce cumene, followed by oxidation of cumene to the corresponding hydroperoxide, and then cleavage of the hydroperoxide to produce equimolar amounts of phenol and acetone. However, the world demand for phenol is growing more rapidly than that for acetone.
Thus, a process that uses higher alkenes instead of propylene as feed and coproduces higher ketones, such as cyclohexanone, rather than acetone may be an attractive alternative route to the production of phenols. There is also a growing demand for cyclohexanone.
It is known from, e.g., U.S. Pat. No. 6,037,513, that cyclohexylbenzene can be produced by contacting benzene with hydrogen in the presence of a bifunctional catalyst comprising a molecular sieve of the MCM-22 type and at least one hydrogenation metal selected from palladium, ruthenium, nickel, cobalt, and mixtures thereof, that the resultant cyclohexylbenzene can be oxidized to the corresponding hydroperoxide which can then be decomposed to produce phenol and cyclohexanone in the presence of an acid such as sulfuric acid in a cleavage step. This cyclohexylbenzene-based process for co-producing phenol and cyclohexanone can be highly efficient in making these two important industrial materials.
The effluent from the cleavage step typically contains phenol, cyclohexanone, the acid catalyst, cyclohexylbenzene, and additional contaminants that may be produced as byproducts from the oxidation and/or cleavage step. To obtain pure phenol and cyclohexanone, the cleavage effluent can be treated first by a basic material, such as an amine (e.g., pentane-1,5-diamine; hexane-1,6-diamine; hexane-1,5-diamine; 2-methylpentane-1,5-diamine; ethylene diamine; diethylene triamine; triethylene tetramine; propylene diamine; and the like), typically in liquid phase under the operation conditions, to neutralize at least a portion of the acid catalyst. The neutralized cleavage effluent can be then separated by, e.g., a distillation column. Because phenol and cyclohexanone forms an azeotrope, complete separation of phenol from cyclohexanone to obtain two pure products can be achieved only with the aid of an extractive distillation solvent. It has been found that, the presence of sulfur and/or acid in the feed into the distillation columns, including but not limited to the extractive distillation column, can significantly hamper the effective separation and/or operations of the distillation column(s), leading to the presence of unwanted contaminants in one or both of the cyclohexanone and phenol products.
Thus, there are needs for (i) a process for effectively separating a mixture comprising cyclohexanone, phenol, cyclohexylbenzene, and a sulfur-containing component to obtain high purity cyclohexanone and/or phenol, and (ii) a process for making phenol and/or cyclohexanone form an extractive distillation feed comprising phenol and cyclohexanone to obtain high purity phenol and/or cyclohexanone. The present invention satisfies these needs.